Expression ratio of xyr1 to steady-state sar1 reference gene in strains RUT C30 (open bars), PX41 (shaded bars), and PXAi20 (filled bars) pre-grown with glycerol as a carbon source and then transferred into glucose (Glc) or cellulose (Cel) medium for 8 or 48 h. RUT C30: parental strain; PX41: recombinant strain constitutively expressing xyr1 under the control of the pdc (encoding pyruvate decarboxylase) promoter; PXAi20: recombinant strain with both xyr1 over-expression and ace1 downregulation. Error bars indicate standard deviations